1. Field of Invention
The present invention relates to a surface acoustic wave device in which a surface acoustic wave element and an electronic component that drive controls the surface acoustic wave element are packaged.
2. Description of Related Art
Recently, surface acoustic wave devices (hereinafter referred to as xe2x80x9cSAW (surface acoustic wave) devicesxe2x80x9d) have been used as resonators or bandpass filters, etc. in electronic components and communication components of mobile telephones and TV receivers, etc.
FIG. 8 is a schematic showing an example of a related art SAW device 1. The SAW device 1 is described with reference to FIG. 8.
The SAW device 1 of FIG. 8 has a substrate 2, a cover 3, an electronic component 5 formed of IC chips, etc. and a SAW element 6, and other elements. A hollow component 2a is formed in the substrate 2. The electronic component 5 and the SAW element 6 are mounted in the hollow component 2a, e.g., with an epoxy adhesive. The cover 3 is arranged on the opening of the hollow component 2a and is joined to the substrate 2 with a sealant or by seam welding. Therefore, the electronic component 5 and the SAW element 6 are in a hermetically sealed state via the substrate 2 and the cover 3.
The SAW element 6 and the electronic component 5, such as semiconductor chips that drive control the SAW element, are arranged side by side in the hollow component 2a. Printed wirings 4 of a predetermined pattern are formed at the bottom of the substrate 2, and the electronic component 5 and the SAW element 6 are electrically connected to the printed wirings 4, e.g., by wire bonding, etc. respectively, thereby electrically connecting the electronic component 5 and the SAW element 6.
FIGS. 9(A)-9(E) are perspective views showing steps of an exemplary related art manufacturing method of a SAW device. The manufacturing method of the SAW device is described with reference to FIG. 9.
First, as shown in FIG. 9(A), printed wirings 4 are formed in a predetermined pattern at the bottom of a hollow component 2a in a substrate 2.
Then, as shown in FIG. 9(B), an electronic component 5 is mounted at the bottom and electrically connected to the printed wirings 4, e.g., by wire bonding, etc.
Subsequently, as shown in FIG. 9(C), a SAW element 6 is mounted at the bottom and electrically connected to the printed wirings 4, e.g., by wire bonding, etc.
Next, as shown in FIG. 9(D), the frequency adjustment of the SAW element 6 is performed. More specifically, a plasma, for example, and the like are irradiated from the opening 2b of the substrate 2 onto the SAW element 6, and a piezoelectric substrate or electrodes formed on a piezoelectric substrate of the SAW element 6 are etched. This frequency adjustment is performed while the SAW element 6 is driven by the electronic component 5. Then, the operation is performed until a desirable frequency characteristic of the SAW element 6 is obtained.
Subsequently, as shown in FIG. 9(E), a cover 3 is arranged on the opening of the substrate 2, and the substrate 2 and the cover 3 are joined with a sealant, thereby hermetically sealing the inside of the hollow component 2a to complete a SAW device 1.
In the related art SAW device 1 of FIG. 8, the electronic component 5 and the SAW element 6 are arranged side by side. Namely, the electronic component 5 and the SAW element 6 are arranged in the same space, i.e., within the hollow component 2a. 
In this instance, if the SAW device 1 is actuated, the electronic component 5 emits heat. The heat emitted from the electronic component 5 is directly transmitted to the SAW element 6 via the atmosphere and the bottom in the hollow component 2a of the substrate 2. The heat greatly affects the temperature characteristics of the SAW element 6 and causes a problem, i.e., that the SAW element 6 cannot display a desirable frequency characteristic.
On the other hand, a so-called two-stage superposed package structure has been proposed as a method for mounting an electronic component 5 and a SAW element 6 in different spaces. When frequency adjustment is performed in a state in which the SAW element 6 is driven by the electronic component 5, however, the process of mounting the electronic component 5 and the SAW element 6 on the packages, respectively, and the process for adhesion and conduction of respective packages must be performed, thereby complicating the manufacturing process.
Accordingly, the present invention addresses the problem referred to above, and provides a SAW device and a manufacturing method thereof which enhances reliability and yield.
The invention in accordance with a first aspect of the invention provides a surface acoustic wave device having a surface acoustic wave element and an electronic component that drive controls the surface acoustic wave element, provided with a first substrate, which has a first connecting terminal having a first hollow component formed therewith, including an opening that accommodates the electronic component and electrically connected to the electronic component formed in the first hollow component, and a second connecting terminal formed in the vicinity of the opening and electrically connected to the first connecting terminal, and a second substrate, which is mounted so that one face side is joined to the opening of the first substrate, and the other face side allows the surface acoustic wave element to be electrically connected to the second connecting terminal, and a cap which is joined to the first substrate and has a second hollow component that hermetically seals the surface acoustic wave element.
In accordance with the structure of the first aspect of the invention, the first hollow component is formed in the first substrate, and the electronic component is mounted in this hollow component. On the other hand, the second substrate has a structure such that one face side is joined to the first substrate, and the surface acoustic wave element is mounted to the other face side. Then, the cap, that seals the surface acoustic wave device in the second hollow component is joined to the first substrate.
Thus, only the electronic component is mounted in the hollow component of the first substrate, and the surface acoustic wave element is mounted on the other face side of the second substrate. Namely, the surface acoustic wave element and the electronic component are arranged in separate spaces partitioned by the first substrate and the second substrate. Therefore, for example, when a plasma is irradiated on the surface acoustic wave element, the electronic component is not exposed to the plasma during the frequency adjustment of the surface acoustic wave device. Moreover, the influence of the heat and electromagnetic wave generated when the electronic component is actuated on the surface acoustic wave element can be suppressed to the minimum.
The invention in accordance with a second aspect of the invention provides a surface acoustic wave device in which the first substrate and the second substrate are joined with a sealant on the lateral face side of the second substrate in the structure of the first aspect of the invention.
In accordance with the structure of the second aspect of the invention, the first substrate and the second substrate are in a state in which they are joined with a sealant applied on the lateral face side of the second substrate, thereby surely hermetically sealing the first hollow component of the first substrate.
The invention in accordance with a third aspect of the invention provides a surface acoustic wave device in which the second substrate and the cap are joined to the first substrate with same sealant, respectively in the structure of either of the first or second aspects.
In accordance with the structure of the third aspect of the invention, with the joint of the first substrate and the second substrate and the joint of the first substrate and the cap, hermetic sealing of the first hollow component and the second hollow component can be simultaneously performed under the same treatment conditions by using the same sealant.
The invention in accordance with a fourth aspect of the invention provides a surface acoustic wave device in which the sealant is made of a conductive brazing metal or a conductive adhesive in the structure of any of the first to third aspects.
In accordance with the structure of the fourth aspect, a shielding effect on electromagnetic wave can be obtained if a conductive brazing metal or a conductive adhesive is used as the sealant.
The invention in accordance with a fifth aspect of the invention provides a surface acoustic wave device in which the sealant is made of a glassy material in the structure of any of the first to third aspects.
In accordance with the structure of the fifth aspect, a cost reduction can be sought by using a glassy material as the sealant.
The invention in accordance with a sixth aspect of the invention provides a surface acoustic wave device in which the grounding electrode is formed on one face side of the second substrate in any of the structures of the first to fifth aspects.
In accordance with the structure of the sixth aspect, the grounding electrode is formed on one face side of the second substrate and is in a state that it is placed between the electronic component and the surface acoustic wave element. Therefore, an electromagnetic wave generated when the electronic component is actuated is shielded by the grounding electrode, thereby reducing its influence on the surface acoustic wave element. Particularly, if a conductive brazing metal or a conductive adhesive is used as the sealant, the shielding effect of the grounding electrode can be further enhanced.
The invention in accordance with a seventh aspect of the invention provides a surface acoustic wave device in which the second substrate includes a ceramic single plate in any of the structures of the first to sixth aspects.
In accordance with the structure of the seventh aspect, back lowering of the entire surface acoustic wave device can be sought by using the ceramic single plate as the second substrate. The thermal expansion coefficients can be made consistent by forming the first substrate and the second substrate from the same material.
The invention in accordance with an eighth aspect of the invention provides a surface acoustic wave device in which the electronic component are flip-chip mounted to the first substrate in any of the structures of the first to seventh aspects.
In accordance with the structure of the eighth aspect, back lowering of the entire surface acoustic wave device can be sought by flip-chip mounting the electronic component to the first substrate.
The invention in accordance with a ninth aspect of the invention provides a surface acoustic wave device in which the surface acoustic wave element is mounted to the second substrate with an adhesive and the electronic component is mounted to the first substrate with the same adhesive as that used in mounting the surface acoustic wave element in any of the structures of the first to eighth aspects.
In accordance with the structure of the ninth aspect, simplification of the manufacturing processes of the surface acoustic wave device can be sought by using the same adhesive.
The invention in accordance with a tenth aspect of the invention provides a manufacturing method of the surface acoustic wave device having a surface acoustic wave element and an electronic component that drive controls the surface acoustic wave element, in which the electronic component is mounted in the first hollow component of the first substrate with an opening, the second substrate with the surface acoustic wave element mounted is aligned in the opening of the first substrate as well as the electronic component and the surface acoustic wave element are electrically connected, the frequency adjustment of the surface acoustic wave element is performed, the cap with the second hollow component is arranged on the first substrate so as to accommodate the surface acoustic wave element in the second hollow component, and the first substrate and the second substrate, and the first substrate and the cap are joined with a sealant, respectively, to seal the electronic component and the surface acoustic wave element.
In accordance with the structure of the tenth aspect, the electronic component is mounted to the first hollow component of the first substrate from the opening, and the second substrate with the surface acoustic wave element mounted in this opening is aligned. Then, the frequency adjustment is performed by irradiating, e.g., a plasma, etc. on the surface acoustic wave element in a state wherein the surface acoustic wave element is drive controlled by the electronic component. Subsequently, the cap is arranged on the surface acoustic wave device, and the first substrate and the second substrate, and the first substrate and the cap are joined with a sealant, respectively.
Thus, when frequency adjustment is performed, the electronic component is in a state such that it is accommodated in the first hollow component and the first hollow component is closed by the second substrate. Therefore, the plasma, etc. are irradiated only on the surface acoustic wave element, but not on the electronic component in the frequency adjustment step. Moreover, inconvenience caused by irradiating the plasma to the electronic component in the frequency adjustment step can be reduced, minimized or prevented.
The invention in accordance with an eleventh aspect of the invention provides a manufacturing method of the surface acoustic wave device in which the second substrate is arranged in the opening of the first substrate in a state such that the sealant is applied on the lateral face side of the second substrate in the structure of the tenth aspect.
In accordance with the structure of the eleventh aspect, the first substrate and the second substrate are joined with a sealant applied on the lateral face side of the second substrate. This enables surely isolating the first hollow component and the second hollow component of the first substrate.
The invention in accordance with a twelfth aspect of the invention provides a manufacturing method of the surface acoustic wave device in which the grounding electrode made of a conducting material is formed on the joint face with the first substrate at the second substrate in the structure of either of the tenth or eleventh aspects.
In accordance with the structure of the twelfth aspect, a grounding electrode is formed on one face side of the second substrate, and is in a state such that it is placed between the electronic component and the surface acoustic wave element. Therefore, an electromagnetic wave, generated when the electronic component is actuated, is shielded by the grounding electrode, thereby reducing its influence on the surface acoustic wave element.
The invention in accordance with a thirteenth aspect of the invention provides a manufacturing method of the surface acoustic wave device in which the same sealant is used as the sealant that joins the first substrate and the second substrate and the sealant that joins the first substrate and the cap in any of the structures of the tenth to twelfth aspects.
In accordance with the thirteenth aspect of the invention, when the first substrate and the second substrate are joined and the first substrate and the cap are joined, hermetic sealing of the first hollow component and the second hollow component can be simultaneously performed under the same treatment conditions by using the same sealant.
The invention in accordance with a fourteenth aspect of the invention provides a manufacturing method of the surface acoustic wave device in which the brazing metal or the conductive adhesive is used as the sealant in any of the structures of the tenth to thirteenth aspects.
In accordance with the structure of the fourteenth aspect, if the brazing metal or the conductive adhesive is used as the sealant, the shielding effect on the electromagnetic wave can be obtained.
The invention in accordance with a fifteenth aspect of the invention provides a manufacturing method of the surface acoustic wave device in which the sealant is made of a glassy material in any of the structures of the tenth to thirteenth aspects.
In accordance with the structure of the fifteenth aspect, if the glassy material is used as the sealant, a cost reduction can be obtained.
The invention in accordance with a sixteenth aspect of the invention provides a manufacturing method of the surface acoustic wave device in which, when the electronic component is mounted to the first substrate, the mounting is performed by flip-chip bonding in any of the structures of the tenth to fifteenth aspects.
In accordance with the structure of the sixteenth aspect, back lowering of the entire surface acoustic wave device can be sought by flip-chip mounting the electronic component to the first substrate.